Bevel gear making

ABSTRACT

A bevel gear making machine is provided with a structural orientation of cradle housing, cradle, tool holder and workhead assembly wherein the tool is designed to rotate about a generally horizontal axis while the work is designed to rotate about a generally vertical axis, and wherein supporting side wall members are provided for securely holding the workhead assembly against vibration during cutting operations. This orientation of these parts may be provided at two cutting stations to constitute a unitary double machine, and such a double machine may be adapted either for two roughing or two finishing operations. Further, two of these double machines may be arranged so as to provide four adjacent cutting stations, two for roughing and two for finishing. In combination with the structure mentioned above, a control arrangement is provided for the generating train whereby a higher production rate is possible. The control arrangement and the cutting tool are provided with their own separate power sources, independent of the generating train power source, and the control arrangement for the generating train is separate from the generating train itself.

United States Patent [72] Inventors ErnstJ.Hunkeler Fairport; Felix P.Wrubleski, Rochester, N.Y. [21] AppLNo. 764,212 [22] Filed 0ct.1,l968[45] Patented Jan. 5,1971 [73] Assignee The Gleason Works Rochester,N.Y.

a corporation of New York [54] BEVELGEAR MAKING 15 Claims, 6 DrawingFigs.

[52] U.S.Cl 90/5,90/1 [51] Int.Cl. B23f9/l0 [50] FieldolSearch..90/5,6,9.4, 3, l

[56] References Cited UNITED STATES PATENTS 1,383,707 7/1921 Famum90/5-X 2,509,660 5/1950 Wingren..., 90/5-X 2,736,238 2/1956 Moncrieff90/1 2,947,223 8/1960 Carlsen etaL. 90/5 3,288,031 11/1966 Krasteletal90/5 3,354,782 11/1967 Buchananetal. 90/1 Primary Examiner-GilWeidenfeld Attorneys-Cushman, Darby and Cushman and Morton A.

Polster ABSTRACT: A bevel gear making machine is provided with astructural orientation of cradle housing, cradle, tool holder andworkhead assembly wherein the tool is designed to rotate about agenerally horizontal axis while the work is designed to rotate about agenerally vertical axis, and wherein supporting side wall members areprovided for securely holding the workhead assembly against vibrationduring cutting operations. This orientation of these parts may beprovided at two cutting stations to constitute a unitary double machine,and such a double machine may be adapted either for two roughing or twofinishing operations. Further, two of these double machines may bearranged so as to provide four adjacent cutting stations, two forroughing and two for finishing.

ln combination with the structure mentioned above, a control arrangementis provided for the generating train whereby a higher production rate ispossible. The control arrangement and the cutting tool are provided withtheir own separate power sources, independent of the generating trainpower source, and the control arrangement for the generating train isseparate from the generating train itself.

PATENTEUJAN slsn a 3552.261 I SHEET 1 or a INVENTO S ERA/57:]: Hum/(4 654 m F? MAY/6458K BYM J14 ATTORNEYS I PATENTEUJAN 5m 3552.261

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, 1 never. can mronc The present-invention relates to gear makingapparatus and particularly to machines for making bevel gears.

' veying gears or gear blanks to the cutting stations and transferringthem between cutting stations with novel means for automatic stockdivision in going from one station to the other, a

novel control means for controlling the operation of the work loadingand unloading and automatic stock division mechanisms, a novelchamfering means designed to remove burrs, etc. from the roughed gears,'and other novel structures and techniques, all of which are beingcovered in a series of patent applications. These applications are: Ser.Nos. 164,213; 764,2l4; 764,22l; 764,222; 764,217; 764,218; 764,2l9;'764,220; 764,2l and 764,2l6. filed of even date herewith, and thedisclosures of which are all incorporated While the present developmentrelates especially to the production of bevel pinion gears for theautomotiveindustry, for example, spiral bevel or hypoid gears,it will beapparent to those skilled in the art that features of the developmentmay be used in machines for making other types of gears, and forindustries other than the automotive industry.

It is a primary general object of the present invention to provide'bevelgear making apparatus with novelstructures and features that willincrease'the production rate of the apparatus over previousmachineswhile at the same timesatisfying the requirements forqualityland precision in the final product. A further general object ofthe invention is'to provide a novel basic design for a single gearmaking machine and which canbe incorporated into gear cutting machinesmounted'or constructed as a double gear cutting apparatus wherein gearcutting operations are performedfat two stations simultaneously. It isintended that the basic design, referred to, will enable the productionof bevel gears to become more automated.

It is contemplated that the double-gear cutting apparatus, referred toabove, can be utilized either for two roughing operations, or it couldbe used with certain structural modifications thereto, 'as will bedescribed h'ereinbe'low, for two finishing operations. It is furthercontemplated-that a double rougher and a double finisher,embodyingthepresent invention, could be utilized together presenting four'cuttingstations, two for'roughing and two for finishing, and with suitablemeans for conveying the work to these various stations to provide a morefully automated operation wherein gear cutting can be going onsimultaneously at both stations in each double machine.

It is still further contemplatedthata double rougher or don-- blefinisher embodying thepresent invention. could be utilized and inopposed or facing relation with each other, with means being providedfor conveying work to the machine, and with means for transferring thework from the conveying means to the, first cutting station and then tothe second cutting station, and finally to an output station, for'eXample, back on the conveyor means.

A further related object is to provide two double gear cutting machines,each of the same basic design and with the same novelstructuralorientation,'referred to, wherein two roughing operations are performedat the first machine,'and two finishing operations are performed at thesecond machine. These two machines, in the illustrative embodiment shownand described herein, are both of generally rectangular outline and arearranged in side-by-side relation so as to facilitate transfer of thework from one machine to the other.

As will be understood, itis necessary in the generation of bevel gearsto provide-a generating train or the like to effect the desired'rollbetween work and tool for proper cutting action. A further object of thepresent invention is to provide a novel combination of novel controlmeans for the generating train with the novel structural orientation ofthe cradle housing cradle, tool holder, workhead assembly and associatedstructures whereby the time for the rolling action in each cutting cyclemay be decreased and the speed of rotation of the tool increased to cutdown the production time for completing the cutting cycle. In theillustrative embodiment of the invention, the control means is in theform of a servomechanism having its-own source of power independent of'the power source for the generating train.

It is a still further object of the invention to provide a novel processor technique of producing finished bevel gears wherein four separategear cutting stations are provided in two double machines, one'forroughing and one for finishing. Thus, a continuous single productionline may be provided wherein the work is fed sequentially through fourcutting stations wherein two roughing operations will be performed byone double machine, and two finishing operations will be performed onthe other double machine. It is contemplated that the two roughingoperations may be continued even if there is a stoppage for some reasonin the finishing machine, and likewise the finishing machine can beoperated even if there is a stoppage for some reason in the roughingmachine.

The foregoing and other objects and advantages of the invention willappear from the following description of the preferred embodimentillustrated in the accompanying drawings, wherein: g

FIG. 1 is a perspective view of a double gear cutting machine embodyingthe invention, and with some of the parts not shown for convenience ofillustration;

FIG. 2 is a somewhat schematic, plan view, on a reduced scale, of asingle gear cutting machine embodying certain features of the invention;

with existing gear roughing or finishing machines so that, for example,a double rougher may be'utilized for producing.

roughed-gears which could then'be finished on existing machinery, or adouble finisher could be utilized with existing roughing machines forthe purpose of finishing the gears produced by those roughing machines:It is also contemplated that a double machine, embodying the invention,could be designed so that one station does roughing and the other doesfinishing, as will be understood by those'skilled in the art.

A further, more specific object of the invention is to provide a gearcutting machine with a novel structural orientation for the cradlehousing, cradle, tool holder, workhead assembly and associatedstructuresto enable the machine to operate at higher speed and with agreater production rate. A related object is to provide a double gearcutting machine presenting two gear cutting stationswherein each-cuttingstation involves this novel structural orientation. The cutting stationsin the double machine preferably are 'rnounted on'a base or frame FIG. 3is a somewhat schematic, plan view, on a reduced scale,'of a double gearcutting machine embodying certain features of the invention; I

FIG. 4 is a somewhat schematic, plan view, on a reduced scale, showingtwo double gear cutting machines embodying certain features of theinvention;

FIG. 15 is an enlarged diagrammatic view illustrating somewhatschematically the generating train and the control means thereforeembodying certain features of the invention;

FIG. 6 is an isometric and diagrammatic view of the generating train andcontrol means therefore illustrated in FIG. 6.

. Referring now .to the drawings, a double gear cutting machineembodying the present invention is shown in FIG. 1. This machine is adouble finishing machine, wherein each of the cutting stations does afinishing operation. However, it will be understood that a doubleroughingmachine embodying the invention may have a similar externalappearance and the same basic design with certain structuralmodifications adapting it for roughing, rather than finishing, as willbe understood to those skilled in the art and as will be apparent fromthe series 6: applications being filed contemporaneously herewith.

".The'double finishing machine is identified by numeral 20 and 2412 24c24d and each machine comprises a frame 26a 26b on which the cuttingstations are presented. A single machine 28 is shown in FIG. describedin some detail, it being understood that like reference numerals will beutilized to designate corresponding parts of the double roughing andfinishing machines shown in 2 and will now be FIG. 4. The single machine28 can be built for use as a rougher V for rough cutting of the work, orwith somewhat different invternal mechanisms, it can be built -as afinisher capable of finishinga previously roughed gear blank. it may bebuilt as shown for manual loading of the work, or equipped for automaticloading using an additional loader attachment (not shown). i.

FIG. 2 illustrates what is called the left side" version and it 1includes the frame 26c, on which is mounted a cradle housing =30containing the cradle 32 and tool holder 34. The tool holder 34 ismounted for rotation within the cradle 32 and detail and claimed in thecopending application Ser. No.

764,222. The tool holder, as will be understood, is designed to mount arotary face mill cutter. The rotary tool holder, face ;mill cutter, andadjustable means in the, cradle for adjusting the position and angle ofthe face mill cutter and rotary tool holder may be conventional, asdisclosed, for example, in US. Pat. No. 2,667,818. M

The single machine .2 8 shown in FIG. 2 als oincludes upstanding flangesor sidewalls 36, 38 suitably mbunted' on the frame 260 and extendingupwardly therefromin straddling relation to the cradle 32. As best seeninjFlG. 1, these sidewalls 36 terminate at a point intermediate theheight of the cradle 32. A workhead assembly 40 is mounted between these'sidewall members 36, 38 and includes a rotatable work holder 42 mountedtherein and designed to receive the work to be cut so that the workisrotatable about a vertical or generally vertical axis. The workheadassembly 40 and the structure for mounting the workhead assembly in themachine are disclosed and claimed in the copending application Ser. No.764,221. As is disclosed in that application, the workhead assembly 40is designed to be reciprocated back and forth in a horizontal directionboth toward and away from the cradle and tool holder. The workheadassembly is also designed to be pivoted or rotated through a limitedangle and about a horizontal axis extending between the sidewall members36, 38, and it will be I adjustable in a vertical direction inconnection with initial setup of the machine, again as is described inthe copending application. Additional structures disclosed in thatapplication also include means for securely clamping or holding theworkhead assembly and work in a firm and secure position during thecutting operations so as to resist vibrations or other undesirablemotions that might otherwise be imparted between the work and tool.

- rotate the tool at a higher r.p.m. so that ,the time for the cuttingcycle for each tooth may be reduced.

The same basic structural orientation ust described, and

shown in FIG. 2, will be seen to be included in each cutting station inthe two double machines 20, 22. Additionally, the

A double machines are shown as including conveyor means 44a, 44biforfeeding pinion gear blanks, or pinion gears which have been roughed tothe machine, and work loading and u'riload- I ing, turret likestructures 46a, 46b are also provided for autonratically transferringthe work from theconveyor means 44a,

copending applicati'tin, Serf, indicated schematically by U @reli"'riumefral'BO mama" FIG. 4.as being associated withth'e aiw=yr mans=majacent the double roughing mach' s ze; and it willoperatc'to removeburrs, sharp points;etcffr3ili il i'e gear t e'e'tli'fas will beunderstood. Such a chamferir'ig ine'ans ls' disclosedand claimed in thecopending application Ser No. 764,21 6.

While the conveyor means 44a, are-snowman no.4 extending the samedirectiomfof'each machine, it viillbe' understood that they rnayextendiipposite directions, for "each machine, or they may extend in'othersuitabl di'rectibns, as toward each other, as.desir'ed. Furthenn'ore,theichii'mfering means 50 may be at any suitablc location or any desiredlocation, and suit ah fadditional conveyor rneans'( not shown) may beprovided for initially feeding the pinion'gear blanks on to the conveyorrri eans 44a, and then for feedingthe roughed gear blanks frorii'thf gdry'eyor 4451b the conveyor 44b, .and finally for removihg tihe finishedglears frbm the conveyor-,44b to some suitable stbrage location, or thelike. Thus,

' the entire operation may befiillyauto r'naticstarting from the formed,involving several combinations and a initial feeding of the pinion gearblanks onto the'conveyor'Ma and ending with' the removal ,of ,th hedgears from the conveyor 44b to some suitablejlocatio i Thus, it will beseen that 'thepre ,g H g li'ridividual machines for ya us'gear cuttingoperations,orfor proiiucing a completely finished pinion gearfror'n'anuncutpinio n gear blank. As stated above, the "left side"v versionshownjinFlG. 2

could be used foran individual roughing or finishih g'floperation. Or, arightjsidef versioh fwhich would correspond to virtually a mirror imageof the left'side ve'rsibnl'could combined with the left side machine'bymounting the two cutting stations on a single frame or base, as shown inFIGS 1, 3 and 4 to constitute a double" or twin machine;-

As indicated, one such machine .could be built for use as a doublefinisher, in which case the machine will be constructed and set up forfinishing one side' of the teeth in the left machine and the oppositeside of. the teeth in theright machine. Such a double finisher willincorporate the conveyor and loader and transfer means, referred toabove, foraccepting previously roughed pinions, moving them to the workholding means at one cutting station for the first finishing operation,then transferring the work to the opposite side for the second finishingoperation, and finally transferring it back to the conveyor 44b and thento a receiving station for the finished parts.

Another such double machine will be available as; a two operationrougher in which one side willaccept unbut blanks from the loader andperforma preliminary roughingoperation. This first roughing cut maybe agashing, nonge'nerating cut, or it may involve a generatingaction. Uponcompletion of this operation, the transfer mechanismlwill then move thework to the work holding fixture on the other side of the machine wherea second roughing operation -will.be pergeneration, followingirlhich thepiece will be transferred back to'the conveyor It will be understoodthat in the operation .of;a double machine, it is contemplated thatcutting will be: going on simultaneously on twoseparate work pieces,.oneat each cutting station. f

For high speed production of bevel pinion gears,if,or.example, of thetype that would be utilized on all American passenger cars and manyforeign cars, a complement of two den- 1 'ble or twin machinespreferably will be employed, one for roughing and the other forfinishing, each as described above and arranged in desired relationformass production, such as in sideby-side relation, as shown in FIG. 4,or in some other relation, as will be evident by those skilled in theart.

THE DRIVING ARRANGEMENT It will be understood that in generation ofbevel gears, such as spiral bevel or hypoid gears, there commonly aretwo basic elements, the cradle and the work spindle, both of these beinglocated in a certain spaced relationship with one another and rotatingin a predetermined timed relationship on their respective axes.Conventionally, the cradle carries a rotating, multibladed face millcutter (not shown) whose axis is in adjustable but stationary positionrelative to the cradle, offset from and generally inclined to the axisof the cradle on which it is mounted. The cradle and cutter mountedthereupon represent the imaginary generating gear, as is understood, andthe rotating cutter blade edges represent a tooth of this imaginarygenerating gear, The work spindle carries the work being cut; the cradlecarrying the cutter rotates about the cradle axis in timed relation tothe rotation of the work spindle with the rotating cutter in engagementwith the work. Thus the imaginary generating gear" is said to roll withthe work piece.

The roll proceeds sufficiently to complete the generation of one toothslot (or in some cutting operations, one side of one previously roughedtooth slot), whereupon there is a withdrawal so that the cradle with itscutter and the work are relatively separated one from the other in thedirection of the cradle axis. The rolling motion of both cradle and workspindle is reversed during which time an increment of motion is added tothe work spindle such as to advance (index) the work relative to thecradle by one pitch. At the completion of the reversal of roll, calledthe return, roll, relative cradle axial movement between cradle and workagain occurs to bring the two into cutting position, whereupon a cycleis repeated to cut the following tooth. It will be understood that, ifdesired for certain cutting operations, a cutting action could beprovided on the return roll, after which the cutter and work will berelatively withdrawn, and the work indexed for the next tooth cuttingcycle.

THE GENERATING TRAIN The generating train of the machine, as will beunderstood, is the complete connection between the cradle and workspindle for controlling the relative generating rotation of these twomembers. The illustrative embodiment of the generating train shown inFIGS. 5 and 6 will now be traced. A worm gear 52 is fixed rotationallyto the cradle 32, and this gear is engaged by a worm 54 connected to atelescoping shaft 56 on which is mounted a change gear 58. This is thepoint in the train where there is introduced a set of four change gears,a selection of which governs the ratio of generating roll between thecradle and work. Continuing through this latter set of change gears 60,62, 64 through shaft 66, there is a connection to a suitable indexdifferential gearing 68. Except during the indexing interval, which willbe referred to again hereinbelow, the index differential 68 can beregarded as a simple train of gearing with gear 70 meshing with gear 72which is rigidly connected to gear 74 meshing with a gear therebelowrigidly connected to gear 76 which inturn meshes with gear 78, as shown.Gear 78 is rigidly connected to or integral with bevel gear 80, in turnmeshing with bevel gear 82 connected to shaft 84.

Shaft 84 is keyed for rotation to another bevel gear 86 engaging with amating gear 88 fastened to a shaft 90 which is connected for rotation toa pinion 92 of a hypoid pair. The meshing hypoid gear 94 is rigidlyconnected to the work spindle. As will be understood, the work spindleis connected for rotation in the workhead assembly 40. This completesthe trace of the generating train, that is, the gearing which links andcontrols the relative rotational motion of cradle and work during thegenerating rolls. It will beunderstood that this generating train willbe capable of being rotated in either direction, for the forward andreturn rolls.

THE INDEXING MECHANISM A suitable indexing mechanism 96 will beprovided, and in this connection, reference is made to U.S. Pat. Nos.3,229,552, and 3,283,660, the disclosure of which is incorporated hereinby reference. The teachings of those patents indicate suitable indexingmechanisms that may be utilized in part in connection with thegenerating with the generating train, in the present invention. In anindexing step, the cradle 32 may be considered as fixed againstrotation, and likewise cradle gear 52, worm 54 and related elements ofthe generating train, as will be evident. In the operation of the index96, an index rack 98 will be moved in a direction perpendicular to theplane of the diagram in FIG. 5 and through a fixed distance by asuitable hydraulic piston (not shown). The rack 98 engages a pinion 100which is made to turn exactly one revolution as a result of thecontrolled distance of rack travel. Pinion 100 drives a gear 102 throughan axially engageable and disengageable one tooth clutch 104. During theforward or indexing stroke of the rack, clutch 104 is held in engagementby hydraulic pressure in cylinder 105, as will be understood. One turnof gear 102 produces a corresponding single turn of mating gear 106,which produces one turn of the coaxial and connected change gear 108.During the indexing motion of gears 106 and 108, a locking pawl 110 ismade to disengage from a notch in a locking disc 112 connected to andcorotatable with the gears 106 and 108. At thecompletion of the oneturn, the locking pawl is made to reengage disc 112.

The change gear ratio 108, 114 is so chosen that an appropriaterotational increment is produced in the gear 114, producing in turn theidentical increment in the connected differential spider 116. Spider 116carries the differential pinions around the stationary gear 70. Theaction of the differential is such as to produce a turning of gear 78relative to gear 70, equal to exactly twice the turning increment of thespider 116. The appropriate rotational increment in gear 114, controlledby the index change gear selection, must be such that the amount ofturning of differential gear 78 relative to differential gear 70 willproduce, by way of generating train elements 78 through 94, an incrementof work spindle turning relative to the fixed cradle equal to one pitchof the work.

It will be recalled that for the purpose of explaining the function ofthe indexing mechanism, the cradle was considered as fixed rotationally.In actual operation, however, the indexing can be made to occur whilethe cradle is turning as, for example, during the noncutting portion orreturn roll of the cycle. The increment of index rotation produced inthe work relative to the cradle is the same.

At the completion of one indexing step, hydraulic pressure in cylinder105 will be released permitting disengagement of clutch 104 and the rack98 and pinion 100 will be returned to their original position, beforethe clutch is reengaged.

THE DRIVE FOR THE GENERATING TRAIN As shown in FIGS. 5 and 6, the drivefor the generating train includes a reversible hydraulic motor 118,driving through shaft 120 and roll change gears 122, 124 and fixedgearing 126, 128, the latter gear being rigidly attached to shaft 66 inthe generating train. A controllable displacement, hydraulic pump 132 isshown as being connected to the hydraulic motor for controlled andreversible driving actuation thereof in conventional manner. The pump132, in turn, is driven by a motor 134, which in the illustrativeembodiment is a constant speed electric motor. The electric motor 134,hydraulic pump 132, and hydraulic motor 118 and the various drivingconnections therefore may all be of conventional design.

CONTROL SYSTEM FOR THE DRIVE TRAIN The present invention contemplates anovel control system for the drive train in combination with the novelstructural orientation of the cradle housing, cradle, tool holder andworkhead assembly, as referred to above. The control system, per se, ismore fully disclosed and claimed in the copending application Ser. No.764,2 l 3.

The illustrative embodiment of the control system, as best seen in FIGS.and 6, includes a servomechanism 136, comprising a variable speed DCmotor 138 driving through belt 140 and pulleys 142, 144, and throughright angle gearing 146, 148 to a worm 150 which in turn is drivinglyengaged to a worm wheel 152. The worm wheel 152 is fixed to and rotatesmain cam shaft 154 which is mounted for rotation suitably in a I feedcam bracket (not shown) rigidly attached to the machine frame. The feedcam shaft 154 carries the feed cam 156, various hydraulic 158 andelectrical 160 trip cams (for various purposes, such as producingappropriate timing for such functions as hydraulic pressure and releaseto the indexing mechanism, ratio control and various set overs as willbe understood). A rise end cam, called a roll cam 162, is also driven bythe cam shaft 154. The variable speed motor 138 will be adjusted toregulate the cycle time of the entire machine. In the present embodimentof the invention, one turn of the main cam shaft 154 will produce onetooth cutting cycle.

. A roll cam follower roller 164 is mounted on a nut 166 of a 'nut andscrew 168 assembly, constituting a differential connection between thecam shaft 154 and the generating train, as will be apparent. The nutwill be constrained against rotation but is free to translate or moveaxially. The screw 168 is free to translate axially and to rotate withinthe nonrotating nut 166, and the lower end of the screw, as shown in thedrawing, bears on or against a pivoted lever 170, the free end 172 ofwhich is arranged to actuate a hydraulic control valve system 173, ofconventional design, and which includes a wobble plate valve (notshown). The wobble plate valve is designed to govern the direction andflow rate of the discharge of the pump to the hydraulic motor, and thisestablishes the direction and rate of motor rotation, as is understood.

A compression spring 174 is shown continuously urging the actuator 170and screw 168 upwardly, as shown in FIG. 5, so as to urge the follower164 into engagement with the roll cam 162.

When the cam 162 rotates from the position shown in FIG. 5, the follower164, nut 166, screw 168 and actuator 170 will tend to move upward, asviewed in FIG. 5, as urged by the spring 174.

This movement will result in a valve movement permitting the pump todischarge fluid (for example, oil) at a certain rate and such as torotate the motor 118 in the direction shown by the arrow. Fixed forrotation. with the motor output shaft 120 is a gear 176 which is engagedto gear 178 fixed for rotation with screw 168. Rotation of the motorresulting from movement of the pump control valve regulating flow of thedriving fluid to the motor will thus effect rotation of the screw 168through the gears 176, 178, such that the screw 178 will thread itselfdownward within the nut 166 and tend to restore the lever 170 andcontrol valve 173 to their original or neutral position. The lever andcontrol valve will be restored to that neutral position unless furtherfalling of the cam path, permitting further upward movement of the nut166, results in a command for continuous discharge from the pump 132 tothe motor 118. The pump 132 and motor 118 will both be of the positivedisplacement type, in the illustrative embodiment, and thus it will beseen that a given rise or fall of the cam will produce a correspondingfixed number of turns of the motor 118, and the established rise of thecam 162 will produce a fixed number of turns each way of the shaft 120per tooth cutting cycle. I

Selection of the appropriate roll change gears 122 and 124 produces fromthe fixed number of turns of the shaft 120 a desired angle of turning inthe work spindle, as required to fully generate one tooth contour.Selection of the ratio of roll change gears 58, 60, 62 and 64 in thegenerating train will produce the proper proportionate angle ofcradleturning, as.

will be apparent. Thus, by suitable choice of these roll change gearsand ratio of roll change gears the desired amount of roll for the workspindle and cradle can be predetermined, for example, depending upon therequirements of a particular cutting operation and cycle. However, thepresent development also contemplates a separate and novel means foreffecting a change in this ratio of 16" between the cradle and workspindle during operation so as to produ'cea different ratio of roll inone direction of roll than in the other direction of roll, as may bedesired for certain cutting operations, for example,

in the generation of spiral or hypoid pinion g'earsuThis means forchanging the ratio of roll, separate from the ratio of roll change gearsmentioned above, is more fully disclosed and claimed in the copendingapplication Ser.-No.- 764,214i

The feed cam 156, operatingfrom the main-cam shaft 154 for cyclecontrol,,preferably is arranged to actuate the cradle 32 axially intoand out of generating position with the work, and in general this willtakeplace, once per cutting cycle, as will be understood. The structurefor effecting this axial movement of the cradle is disclosed and claimedin the copending application Ser. No. 764,222.

THE CUTTER DRIVE The cutting tool, tool holder 34, and the cutter drivetrain are shown in FIG. 5 as driven by a separate power source, forexample, an electric motor 177, through speed change pulleys 179, 181and belt 183, and a train of gearing 185 within the cradle. This gearingmay be of conventional design as dis closed, for example, in U.S. Pat.Nos. 2,667,8l8 and 3,288,031. i

HELICAL MOTION AND RATIO CONTROL MECHANISM during a finishing operation.Thus, while both the helical motion mechanism and ratio controlmechanism are shown in the diagram of FIG. 5 for illustrative purposesand for convenience of illustration, it will be understood that bothmechanisms will not be utilized in the same machine at the same time.The ratio change mechanism is disclosed more fully in copendingapplication Ser. No. 764,214.

The helical motion mechanism 186 is designed to effect, from therotational motion of the cradle 32, the cradle axial motion and in timedrelation with the rotation. As shown, this is accomplished by means of agear t'rain, starting a large gear 190, coaxially fixed to the cradlefor rotation therewith, and driving pinion 192, then through a train 194driving a cam 196. The cam 196 operates through a follower mechanism andother structures (not shown) for actuating'the cradle feed yoke 197 toeffect the axial movement, as is disclosed more fully in copendingapplication Ser. No. 764,222. 11 will be understood that this axial feedof the cradle is in connection with a cutting movement, whereas thewithdrawal of the cradle, for example, in connection with indexing, willbe accomplished through the feed cam 156 described above in connectionwith the servocontrol mechanism 136.

The ratio control mechanism l88'of a rougher functions in combinationwith a tooth rough cutting operationin which cutting takes place in thetooth slot during both" the up and down roll, with the brief pause forcradle withdrawal and work index at the end ofthe return roll. For upand down roll roughing, the ratio control mechanism 188 is'e'ngagedduring one roll direction only. While engaged it adds or'subtracts asteady increment of turning to the cradle by moving the cradle worm 54axially, thereby producing adifferent ratio of cradle to work roll. Theratio control mechanism 188, as shown in FIG. 5, includes a train ofgears beginning with gear 198 driven from the gear 176 on shaft 120, andfurther includes hypoid gears 200 and ratio control change gears 202.These rangement (not shown).

latter gears are connected throughgearing 204 to a cam 206 which movesfollower roller 208 and follower 210. The latter movement drives theworm 54. axially, as is disclosed in copending application Ser. No.764,214.

DRIVE CONNECTION WITH THE RIGI'IT SIDE OF A DOUBLE MACHINE The drivearrangements just described and as shown in FIGS. and 6 are designed forthe cutting station at the left side of the machine, and it willbeunderstood that the drive arrangement for the cutting station at theright side in a double machine preferably includes a similar oridentical driving ar- It is contemplated that the timing cycle for thecutting station at the right side of this machine will be controlled bya mechanical connection illustrated as being in the form of athroughshaft 212 from pulley 1 44 and gear 146 to the gears 146', 148'at the right side of the machine, as shown in FIG. 6, such that thecyclecontrol cam shafts l54, 154 for both sides of the double machine aredriven by the variable speed motor 138 at the left side of the machine.

THE LOADER-TRANSFER MECHANISM INCREASE IN PRODUCTION One of the reasonsfor the increase in production provided by the present invention is thatthe cutter may now be operated at a much higher speed, as .indicatedabove. This is possible because, among other things, the cutter driveand gearing have been separated entirely from the generating train, anda novel structural orientation of tool and work holders and supportingstructures has been provided to withstand the higher cutting speeds.Furthermore the control means for the generating train isseparate fromit and is operated, by its own independent power source, while thegenerating trainhas its own separatepower source. This also enables thegenerating train to operate at higher speeds so as to accommodate thefaster cutting cycle. In typical previous machines, the means forcontrolling the operation of the generating train actually drove thegenerating train itself, as disclosed, for example, in U.S. Pat. No.2,667,818. While such structures were and still are satisfactory forcommercial production, the present development is designed to constitutean improvement thereover by providing for an even higher productionrate.

' It thus will be seen that the objects-of this invention have beenfully and effectivelyaccompli shed. It will be realized, however, thatthe foregoing specific embodiment has been shown and described only forthe purpose of illustrating the principles of this invention and issubject to extensive change without departure from such principles.Therefore, this invention includes all modifications encompassed withinthe spirit and scope of the following claims.

We claim:

1. A gear cutting machine comprising a base frame, a cradle housingmounted on said frame, a cradle journaled in said housing for rotationabout a generally horizontal axis, a tool holder mounted in said cradlefor rotation about a generally horizontal axis and above said frame, twoparallel and spaced upstanding side wall support members'attached tosaid frame and extending upwardly therefrom in straddling relation tosaid cutting tool holder; a workhead assembly disposed between andattached to said support members in a position below said tool holder,anmork holder mounted in said workhead assembly for rotation about agenerally vertical axis.

2. The machine as defined in claim 1 and further including a reversinggenerating train operatively connected to said cradle and said workholder for imparting generating rolls thereto, said generating trainincluding a power source with means for driving said train in reversedirections, and a control means separate from said generating train butoperatively connected thereto for controlling operation thereof in bothdirections.

3. The machine as defined in claim 2 wherein a separate power source isprovided for said tool holder.

4. The machine as defined in-claim 2 wherein said control means is aservomechanism having its own separate power source. 1

5. The machine as defined in claim 4 wherein said servomechanismincludes actuator means operatively connected to, said generating trainpower source for controlling the effect of that latter power source onsaid generating train.

6. The machine as defined in claim 5 wherein said generating train powersource includes a hydraulic motor and a hydraulic pump with meansconnecting said pump to said motor to drive the latter in reversedirections, and said servomechanism controlling the effect of said pumpon said motor.

7. A gear cutting machine as defined in Claim 1 wherein said cradle,tool holder, and workhead assembly define a first cutting station andfurther including a second cutting station spaced from said firstcutting station, said second cutting station comprising: a second cradlehousing mounted on said frame, a second cradle journaled in said housingfor rotation about a generally' horizontal axis, a second tool holdermounted in said cradle for rotation about a generally horizontal axisand above said frame, two-spaced and parallel upstanding side wallsupport members attached to said frame and extending upwardly therefromin straddling relation to said second tool holder, a second workheadassembly disposed between and attached to said last-named supportmembers in a position below said second tool holder, and a second workholder mounted in said second workhead assembly for rotation about agenerally vertical axis, said first-named two support members and saidsecond-named two support members being generally coplanar.

8. The machine as defined in claim 7 wherein said frame is of generallyrectangular outline in plan view with said cutting stations beingdisposed at opposite endsof said frame with the two tool holders facingeach other and with the workhead assemblies being disposed intermediatethe tool holders.

9. The machine as defined in claim 7 and including a reversinggenerating train for each cutting station and operatively connected tosaid cradle and said work holder at that station for impartinggenerating rolls thereto, each of said generating trains including apower source with means for driving said train in reverse directions,and a control means separate from said generating train but operativelyconnected thereto for controlling operation thereof in both directions.

10. The machine as defined in claim 9 wherein a separate power source isprovided for said tool holder, and wherein said control means is aservomechanism having its own separate power source.

11. The machine as defined in claim 10 wherein said servomechanismincludes actuator means operatively connected to said generating trainpower source for controlling the effect of that latter power source onsaid generating train.

12. The machine as defined in claim 1l wherein said generating trainpower source includes a hydraulic motor and a hydraulic pump with meansconnecting said pump to said motor to drive the latter in reversedirections, and said servomechanism controlling the effect of said pumpon said motor.

13. Gear cutting apparatus including a second machine as defined inclaim 7 disposed adjacent to said first machine.

14. The apparatus as defined in claim 13 wherein said machines are ofgenerally similar outline with said base frames 3 ,5 52,261 1 l 12 beingof generally rectangular outline in plan view and cutting stations oneach of said rnaehines areal-ranged in opwherein said machines arearranged with said base frames in positely facing relation and wherein'said four Cutting statibnS generally parallel, juxtaposed relation. arearranged to constitute corners of a generally rectangular l 5. Theapparatus as defined in claim 14 wherein the outline.

1. A gear cutting machine comprising a base frame, a cradle housingmounted on said frame, a cradle journaled in said housing for rotationabout a generally horizontal axis, a tool holder mounted in said cradlefor rotation about a generally horizontal axis and above said frame, twoparallel and spaced upstanding side wall support members attached tosaid frame and extending upwardly therefrom in straddling relation tosaid cutting tool holder, a workhead assembly disposed between andattached to said support members in a position below said tool holder,and a work holder mounted in said workhead assembly for rotation about agenerally vertical axis.
 2. The machine as defined in claim 1 andfurther including a reversing generating train operatively connected tosaid cradle and said work holder for imparting generatinG rolls thereto,said generating train including a power source with means for drivingsaid train in reverse directions, and a control means separate from saidgenerating train but operatively connected thereto for controllingoperation thereof in both directions.
 3. The machine as defined in claim2 wherein a separate power source is provided for said tool holder. 4.The machine as defined in claim 2 wherein said control means is aservomechanism having its own separate power source.
 5. The machine asdefined in claim 4 wherein said servomechanism includes actuator meansoperatively connected to said generating train power source forcontrolling the effect of that latter power source on said generatingtrain.
 6. The machine as defined in claim 5 wherein said generatingtrain power source includes a hydraulic motor and a hydraulic pump withmeans connecting said pump to said motor to drive the latter in reversedirections, and said servomechanism controlling the effect of said pumpon said motor.
 7. A gear cutting machine as defined in Claim 1 whereinsaid cradle, tool holder, and workhead assembly define a first cuttingstation and further including a second cutting station spaced from saidfirst cutting station, said second cutting station comprising: a secondcradle housing mounted on said frame, a second cradle journaled in saidhousing for rotation about a generally horizontal axis, a second toolholder mounted in said cradle for rotation about a generally horizontalaxis and above said frame, two spaced and parallel upstanding side wallsupport members attached to said frame and extending upwardly therefromin straddling relation to said second tool holder, a second workheadassembly disposed between and attached to said last-named supportmembers in a position below said second tool holder, and a second workholder mounted in said second workhead assembly for rotation about agenerally vertical axis, said first-named two support members and saidsecond-named two support members being generally coplanar.
 8. Themachine as defined in claim 7 wherein said frame is of generallyrectangular outline in plan view with said cutting stations beingdisposed at opposite ends of said frame with the two tool holders facingeach other and with the workhead assemblies being disposed intermediatethe tool holders.
 9. The machine as defined in claim 7 and including areversing generating train for each cutting station and operativelyconnected to said cradle and said work holder at that station forimparting generating rolls thereto, each of said generating trainsincluding a power source with means for driving said train in reversedirections, and a control means separate from said generating train butoperatively connected thereto for controlling operation thereof in bothdirections.
 10. The machine as defined in claim 9 wherein a separatepower source is provided for said tool holder, and wherein said controlmeans is a servo-mechanism having its own separate power source.
 11. Themachine as defined in claim 10 wherein said servo-mechanism includesactuator means operatively connected to said generating train powersource for controlling the effect of that latter power source on saidgenerating train.
 12. The machine as defined in claim 11 wherein saidgenerating train power source includes a hydraulic motor and a hydraulicpump with means connecting said pump to said motor to drive the latterin reverse directions, and said servo-mechanism controlling the effectof said pump on said motor.
 13. Gear cutting apparatus including asecond machine as defined in claim 7 disposed adjacent to said firstmachine.
 14. The apparatus as defined in claim 13 wherein said machinesare of generally similar outline with said base frames being ofgenerally rectangular outline in plan view and wherein said machines arearranged with said base frames in generally parallel, juxtaposedrelation.
 15. The apparatus as defined in claim 14 wherein the cuttingstations on each of said machines are arranged in oppositely facingrelation and wherein said four cutting stations are arranged toconstitute corners of a generally rectangular outline.